Bohr Diagrams and Lewis Dot Structures

Review Electrons can exist in different energy levels the # of Electrons in an atom are equal to the # of Protons in an atom # of Valence Electrons are the outermost Electrons of an Atom

What You’re about to learn How to draw the Electrons around an Atom in a Bohr Diagram How many Electrons are found in any Element’s Valence Shell How to draw a Lewis Structure

Review A Bohr Diagram is the model of an atom with the Nucleus at the center, and the Electrons drawn around it on different energy levels.

Now for some practice For an Atom of Hydrogen: 1 Electron! Simple, you just draw the first Electron here

Next For an Atom of Helium: 2 Electrons! Simple, you just draw the second Electron here

More For an Atom of Lithium: 3 Electrons! But wait a minute…We said that only 2 Electrons can fit into the first level So What do we do when it’s full????

WE ADD ANOTHER LEVEL!!! That’s right, the first energy level is full Now we add another level!!! This new level can hold up to 8 Electrons!!!

So For an Atom of Lithium: 3 Electrons! Simple, you just draw the third Electron here

Then What? When you run out of room on the second level, you add a third that can hold another 8 2-8-8 Rule!!!!!

You should Know by Now How to draw a Bohr Diagram That the 1st energy level can hold 2 e- The 2nd can hold 8 e- The 3rd can hold 8 e-

LEWIS DOT DIAGRAMS

Lewis Structures All you have to do for a Lewis Structure is draw Dots around an Element’s Symbol But How Many????

So… The amount of dots you draw for a Lewis Structure (LS for short) is equal to the # of Valence Electrons in an Atom

Review: Valence Electrons The # of Valence e- an atom has is dictated by the Group the Element is in Groups are the Vertical Columns on the Periodic Table!!! It’s So Simple!!!!

Lewis Dot Diagrams The Lewis Dot Structure is a bit different from the Bohr model. It only shows the element symbol and it’s outer most electron shell.

Step 1: Write the Element Symbol Step 2: Find the number of electrons in the last energy level of the Bohr Model (Valence Electrons) Step 3: Place the electrons (dots) around the symbol in clockwise order so that there are no more than 2 electrons per side.

Practice: The First Two Are Tricky so pay attention

Practice: All Elements in the first group have only 1 Valence e-

Practice: All Elements in the first group would have a LS like this: H

Practice: All Elements in the second group have only 2 Valence e-

Practice: But what about Helium!!! It only has 2 e- so it can only have 2 e- in its Valence Shell

Practice: All Elements in the second group would have a LS like this He

So… Group 3 3 Valence e- Structure like this: B

Now you should know How to draw the Electrons around an Atom in a Bohr Diagram How many Electrons are found in any Element’s Valence Shell How to draw a Lewis Structure